The goal of this study, the first of its kind, is to examine the occurrence of cardiorespiratory events (in particular, apnea and bradycardia) in infants on home cardiorespiratory monitors in relation to daily measures of ambient air pollution in the Atlanta area. There is substantial evidence regarding the adverse cardiorespiratory health effects of ambient air pollution, but scanty evidence in infants, considered a susceptible subpopulation. By virtue of their access to unique air quality and outcome data, the proposers have an extraordinary opportunity to contribute to understanding the health effects of air pollution in infants. The proposers will make innovative use of an existing outcome data source from the Apnea Center of Children's Healthcare of Atlanta at Egleston. The Apnea Center is the largest such center in the U.S. and is the sole referral center following infants on home monitors in the metro-Atlanta area, providing complete coverage of the Atlanta-area population. Moreover, it is one of few centers (perhaps the only) that stores all data electronically. The infants in this study population who are at high risk for cardiorespiratory events are likely to be an especially susceptible subgroup. The study will utilize a uniquely comprehensive air quality data source from the ongoing Aerosol Research and Inhalation Epidemiology Study that includes gaseous and particulate measures as well as particulate components. The relationship between daily measures of selected pollutants and occurrence of apnea and bradycardia will be analyzed using several methods including case-crossover, panel and time-series approaches controlling for appropriate covariates. Based on the number of infants followed by the Apnea Center to date, the study population will include an estimated 6,300 infant patients with approximately 8,200 recorded apnea events and 21,400 bradycardia events. Use of this novel outcome measure thus provides high power to assess the associations of interest. This study will complement the proposers' ongoing studies that are examining cardiorespiratory events in emergency departments, in patients with automatic implantable cardioverter defibrillators (AICDs), and in adult patients with trans-telephonic event monitors in relation to ambient air pollution in Atlanta. The study is expected to provide important new information regarding health effects of ambient air pollution on high-risk infants.